Joomla is one of the leading open-source Content Management Systems. With a userbase of over 400,000, they use phpBB as a reliable platform for support.
The Raspberry Pi is a cheap, credit-card sized computer. The official website uses phpBB for their discussion forums.
VirtualBox, developed by Oracle, is cross-platform x86 virtualisation software. It has become one of the most widely used virtualisation solutions in the world.
Fujitsu is a hardware and IT services company focused on providing IT-driven business solutions. Their community forum is powered by phpBB.
KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
The VideoLAN project produces the extremely popular VLC media player software. Their forums provide support for users of the software as well as the development community.